The present invention relates generally to head-mounted displays, and more particularly to an improved imaging system for a head-mounted display which weighs less, costs less, displays higher image quality, and exhibits a wider field of view than prior art systems.
A Head-Mounted Display (HMD) is an apparatus worn as a helmet or goggle which presents electronically generated or relayed imagery to the user. In some applications such imagery is optically combined with a direct view of the outside world. In most applications however, the electronic imagery is the only scene presented to the user, creating a virtual reality which the user can scan by head movement. Such virtual reality is useful in many applications such as video games, computer aided design and the remote operation of robots.
All HMD configurations begin with an Electronic Display Device (EDD) such as a Cathode Ray Tube (CRT), a Liquid Crystal (LC) panel or a Light Emitting Diode (LED) array. The EDD is viewed by the eye through an imaging system which produces a virtual image of the EDD apparently focused at a comfortable viewing distance.
The preferred HMD exhibits several important characteristics. First, the HMD should be capable of displaying a wide Field-of-View (FOV) so that the user enjoys the perception of being totally immersed in the virtual reality while also benefiting from the presence of peripheral cues. Second, the HMD should be light-weight so that the user is not overly encumbered--especially during head movement. Third, the HMD must be practically constructed to minimize cost and thereby accommodate the greatest number of applications. Fourth, the HMD should provide images which appear real.
Known HMD imaging systems use a combination of lenses and/or mirrors to directly relay the EDD image to the eye. To achieve an acceptable image quality over a large FOV, such combinations require large compound optics which are expensive, require large amounts of space, and are thick and therefore heavy. Known HMD imaging systems also image the artificial picture element (pixel) and/or line structure of the image produced by the EDD, creating an artificial appearance and therefore reducing realism in the image seen by the eye.